Suppose a situation where, when an own vehicle is traveling in a traveling lane, a second vehicle turns left from a right side road at a forward T-shaped intersection. In this situation, if the second vehicle turns with an excessively large turning radius causing the second vehicle to enter the traveling lane of the own vehicle, the own vehicle and the second vehicle are likely to have a minor collision. With a view to avoiding such a danger, there has been proposed a technique of, when, on a side road located forward of an own vehicle, a second vehicle is detected, predicting a turning trajectory of the second vehicle to enable the own vehicle to automatically perform an avoidance action (see, for example, Patent Document 1).